In a conventional aluminum extrusion operation, aluminum stock in the form of large logs, perhaps 5 to 16 inches in diameter and up to 20–24 feet in length, are fed on a conveyor through an elongated furnace, where they are heated continuously to about 800–950° F. Then the logs are cut into short lengths called billets, which are fed immediately into an extruder, while the billets are hot. The extruder includes a ram that presses the billets through a die that forms the aluminum into extrusions of a desired shape. The extrusions can then be cut into desired lengths. Billets are cut to specific lengths, depending upon the particular part being extruded.
In a conventional aluminum extrusion operation, it is customary to change extrusion dies frequently. Each die requires a billet of a certain length. Thus, it is desirable to cut the logs into billets after they are heated and immediately before they are fed into the extrusion die, so that length can be adjusted as desired just before the billet is needed in the die.
The customary method that has been utilized in the aluminum industry for many years for cutting heated aluminum aluminum logs into billets has been a so-called hot shear, which is a pair of cutting dies that cut the aluminum into billets by a shearing action. One problem with this type of cutter is that a shear tends to compress the ends of the billet slightly by the clamping action of the shears. This gives the ends of the billet a non-circular shape with rounded edges, where the shears exert a clamping and cutting action on the log. This irregular shape can introduce bubbles in an extruded product and sometimes presents difficulties in extruding.
Notwithstanding these problems, the use of shears has been common practice for many many years.
Circular saws have been used to cut cold aluminum logs into billets prior to heating and to cut extrusions after formation. However, to date, circular saws have not been used successfully to cut thick hot aluminum logs into billets immediately after heating in a furnace and prior to extrusion. One reason for this is that hot aluminum has a sticky or gummy texture and would be expected to gum up and accumulate on a saw blade. Also, it would be expected that it would be damaging to saw equipment to position it adjacent the open end of a 1000° F. furnace.
An object of the present invention is to provide an improved method and apparatus for cutting hot aluminum logs into billets for an extruding operation.